The buildings at Belsay (not to mention the Quarry garden) are of national importance. The beautiful honey-coloured 14th century castle, the house of 1614 and Charles Monck's Belsay Hall are of the greatest interest.

Sir Charles Monck began building his magnificent Grecian mansion and associated grounds and gardens in 1807, prompted by the classical buildings he had seen on his honeymoon in Berlin and Athens. Belsay Hall, however, is very different from all other Greek Doric houses in Britain. it is a block exactly one hundred feet square, raised on a podium like a Greek temple. The exterior has a 'pure and noble simplicity' and the colonnaded hall inside is as severe and unique as the exterior.

The house is again of honey-coloured sandstone and is dressed with the most remarkable precision. How the masons achieved this skill is not known, but subsequent to Belsay, Northumbrian masons were renowned throughout the country.